ANGLE OF VlEW - The angular range that can be focused within the image size. Small focal lengths give a wide angle of view, and large focal lengths give a narrow field of view.

APERTURE - The opening of a lens which controls the amount of light reaching the surface of the pickup device. The size of the aperture is controlled by the iris adjustment. By increasing the f stop number (f1.4, f1.8, f2.8, etc.) less light is permitted to pass to the pickup device.

ASPECT RATlO - The ratio of the picture frame width to the picture frame height in standard TV systems. It is 4 units horizontal over 3 units vertical.

AUTOMATlC FREQUENCY CONTROL (AFC) - An electronic circuit used whereby the frequency of an oscillator is automatically maintained within specified limits.

AUTOMATlC GAlN CONTROL (AGC) - An electronic circuit used by which the gain of a signal is automatically adjusted as a function of its input or other specified parameter.

AUTOMATlC lRlS LENS - A lens in which the aperture automatically opens or closes to maintain proper light levels on the faceplate of the camera pickup device.

ATTENUATlON - A decrease or loss in a signal.

BACK FOCUS - An alignment of the rear of the lens to the image device.

BLACK LEVEL - The level of the video signal that corresponds to the maximum limits of the black areas of the picture.

BACK LIGHT COMPENSATION - A feature that automatically adjusts the image to compensate for bright lights, to give more detail on the darker areas of the image. Ex. To focus on the detail of a face of a person that has the sunlight shining from behind.

C MOUNT/ CS MOUNT - CCTV lenses are available in two different lens mounts. "C-mount" lenses have a flange back distance of 17.5mm vs. 12.5mm for "CS-mount" lenses. C-mount lenses can be used on CS-mount cameras by utilizing a 5mm adapter or adjusting the camera for C-mount lenses. Because of the shorter back focal distance, CS-mount lenses can only be used on CS-mount cameras. Your picture will be out of focus if you use a CS-mount lens on a C-mount camera.

CCTV - The common abbreviation for Closed Circuit Television.

COATlNGS - Light is lost by reflection from optical surfaces that are intended to be refractors only. This loss is effectively reduced by very thin coatings on the lens surfaces. This can be seen as a blue or violet hue on the lens surface.

COAXlAL CABLE - A type of cable capable of passing a range of frequencies with low loss. It consists of a hollow metallic shield in which one or more center conductors are put in place and isolated from one another and from the shield.

COMPOSITE VIDEO - A full video signal that combines picture signal and synchronization pulses.

COMPRESSION - Digital video pictures compressed into JPEG, M-JPEG, MPEG and Wavelet.

DECIBEL(DB) - A measure of the power ratio of two signals. It is equal to ten times the logarithm of the ratio of the two signals.

DIGITAL VIDEO RECORDER (DVR) - A device that records video signal digitally.

DC TYPE LENS - An auto-ir is lens with internal circuit which receives voltage and a video signal from the camera to adjust the iris.

DEPTH OF FlELD - The front to back zone in a field of view which is in focus in the televised scene. With a greater depth of field, more of the scene, near to far, is in focus. lncreasing the f-stop number increases the depth of field of the lens. Therefore, the lens aperture should be set at the highest f-stop number usable with the available lighting. The better the lighting, the greater the depth of field possible. In other words, the depth of field is the area in front of the camera which remains in focus. The larger the f-number the greater is the depth of field.

DIGITAL VERSATILE DISK (DVD) - An optical disk the same size as a CD, used for storing video, audio and computer data.

ELECTRONlC SHUTTERlNG - The ability of the camera to compensate for moderate light changes in indoor applications without the use of auto iris lenses.

EQUALlZATlON - The process of correcting losses of certain components in a signal.

FlBER OPTlCS - Flexible glass fibers used to conduct energy. It is valuable in the coupling of multi-stage image intensifiers.

FOCAL LENGTH - The distance from the cente r of the lens to a plane at which point a sharp image of an object viewed at an infinite distance from the camera is produced. The focal length determines the size of the image and the angle of the field of view seen by the camera through the lens. That is the distance from the center of the lens to the pickup device.

FRAME - The total area of the picture which is scanned while the picture signal is not blanked.

GEN-LOCK - A method used to synchronize one or more cameras by external means such as: composite video, composite sync, horizontal or vertical sync.

GAMMA CORRECTION - A variation in the input signal to provide a linear relationship between signal source and display output.

HORlZONTAL RESOLUTlON - The maximum number of individual picture elements that can be distinguished in a single scanning line.

HERTZ(Hz) - Cycles per second.

lMAGE SlZE - Reference to the size of an image formed by the lens onto the camera pickup device. The current standards are: 1", 2/3", 1/2" and 1/3" measured diagonally.

lNClDENT LlGHT - The light that is falling directly over an object.

INFRA RED (IR) - Light waves just outside the visible spectrum; that is, waves slightly longer than those visible to the human eye. This is often used for covert or semi-covert surveillance to provide a light source for cameras to record images in dark.

IP CAMERA - A camera designed to record pictures and transmit directly over a computer in JPEG or MPEG.

IRIS - A mechanical device that allows adjustment to control the amount of light passing through the lens of a camera.

JPEG - A standardized image compression mechanism used in CCTV systems to compress and store individual frames of video. JPEG stands for Joint Photographic Experts Group, the original name of the committee that wrote the standard.

LIQUID CRYSTAL DISPLAY (LCD) - A flat panel technology which uses liquid crystals sandwiched between two glass plates. It is smaller, lighter and has very small power consumption.

LOOPlNG - A term indicating that a high impedance device has been permanently connected in a parallel to a video source.

LUX - Refers to the amount of light required for a camera to capture a good image. Infrared cameras have very low lux.

LAG - The image retention of an object after the object has been scanned. Sometimes, it causes smearing effect.

MANUAL lRlS LENS - A lens with manual adjustment to set the iris opening (F stop) in a fixed position used for fixed lighting applications.

MlNlMUM OBJECT DlSTANCE (M.O.D.) - The closest distance a given lens wi ll be able to focus upon an object. This is measured from the vertex (front) of the lens to the object. Wide angle lenses generally have a smaller M.O.D. than large focal length lenses.

MONITOR - A device used to display the images from your cameras (or captured on your recording device). The two basic kinds used in CCTV applications are analog/composite video monitors, used to display images in analog systems. Digital or VGA monitors are used with digital devices like the Digital Video Recorders.

MONOCHROME - Having only one color. In television it is black and white.

MPEG - A standard for compression and storage of movies or video clips. It stands for Moving Pictures Expert Group .

MULTIPLEXER - A device that can accept a number of camera inputs and almost simultaneously display them on a single monitor and/or record them. Multixplexers can also be used to transmit multiple cameras over the same transmission medium.

NTSC - A standard developed by National Television Systems Committee for the United States color television system. 
PAL - A standard for analog television display used in UK. It stands for Phase Alternating Line

PlNHOLE LENS - A type of lens used for applications where the camera/lens must be hidden. Front of lens has a small opening to allow the lens to view an entire room through a small hole in a wall.

PIXEL - An area on the surface of the imaging device, normally a CCD which converts electrical energy to visible light.

RESOLUTlON - A measure of the ability of a camera or television system to reproduce detail. The higher the resolution, the more detail that can be captured in a picture. Cameras typically capture about 380 horizontal lines of resolution.

ROLL - A loss of vertical sync which causes the picture to move up or down on the TV screen.

SHUTTER - A mechanical device on a camera that opens and closes to control the time of a photographic exposure. The old cameras use mechanical shutters whereas the new ones use electronic circuits to perform the same function.
SlGNAL TO NOlSE RATlO - The ratio between a useful video signal and unwanted noise.

SYNC - Electronic pulses inserted in the video signal for the purpose of assembling the picture information in the correct position.

TEARlNG - A picture condition in which horizontal lines are displaced in an irregular manner.

TRACKlNG - A zoom lens' ability to remain in focus during the entire zoom range from wide angle to telephoto position.

VARI FOCAL LENS - A camera lens in which the focus is not fixed, it can be manually or automatically adjusted.

VlDEO TYPE LENS - An auto-iris lens without an internal circuit to control the iris. All iris control voltages come from a circuit located within the camera.

WAVELETS - A type of compression technique used to offer high compression without degrading the image quality.

ZOOM LENS - A lens system that may be used as a wide angle, standard or telephoto lens by varying the focal length of the lens.

ZOOM RATlO - The ratio of the starting focal length (wide position) to the ending focal length (telephoto position) of a zoom lens. A lens with a 1 OX zoom ratio will magnify the image at the wide angle end by 10 times.

© Copyright 2005. Optima Security Online.